The invention concerns a device for generating ultraviolet radiation with high spectral radiation density, the radiation being produced in a mercury/argon-filled discharge tube with a thermoemissive cathode by a wall-stabilized d.c. gas discharge at a mercury pressure p.sub.Hg between 5 .times. 10.sup.-.sup.3 and 5 .times. 10.sup.-.sup.1 torr, an argon pressure P.sub.Ar between 0.01 and 10 torr and a current density j.sub.o of the discharge current I between 1 and 25 A/cm.sup.2, and the two electrode spaces being connected to one another by a pressure equalization space as well as by the discharge region.
Such a device -- in short: high-current-low-pressure-UV-radiation source-was described in its essentials in main German patent PA 24 12 997.3 (copending U.S. Pat. application Ser. No. 551,425, filed Feb. 20, 1975) where the value of the discharge current I or the current density j.sub.o is adjusted to suit the material to be irradiated, and the mercury pressure is controlled by the mercury temperature in such a way that the yield of the line of wavelength 253.7 .mu.m, i.e. the ratio of the radiation output at this wavelength to the electrical power input to the discharge, is at least 80% of the yield-maximum for the set current density j.sub.o. The quantitative relationship between the set dischargecurrent density j.sub.o and the mercury temperature to be selected is detailed in the main patent.
In the practical form of embodiment given in the main patent the two electrodes, cathode and anode, are enclosed in separate envelopes, preferably of glass. This makes fabrication difficult and makes the device rather delicate for handling in industrial use. If the envelopes are located side-by-side, a more complicated, bulkier and more expensive holder becomes necessary. In certain installations, e.g. in packaging machines for sterile liquid filling in which filling is done through a tube, or in the sterilization of bottles, radiation sources with side-by-side electrode-space envelopes can be incorporated only with great difficulty.